Abstract

The current study aims at characterizing the mechanisms that allow humans to entrain the mind and body to incoming rhythmic sensory inputs in real time. We addressed this unresolved issue by examining the relationship between covert neural processes and overt behavior in the context of musical rhythm. We measured temporal prediction abilities, sensorimotor synchronization accuracy and neural entrainment to auditory rhythms as captured using an EEG frequency-tagging approach. Importantly, movement synchronization accuracy with a rhythmic beat could be explained by the amplitude of neural activity selectively locked with the beat period when listening to the rhythmic inputs. Furthermore, stronger endogenous neural entrainment at the beat frequency was associated with superior temporal prediction abilities. Together, these results reveal a direct link between cortical and behavioral measures of rhythmic entrainment, thus providing evidence that frequency-tagged brain activity has functional relevance for beat perception and synchronization.

SSEPs were measured in response to two auditory rhythms, one syncopated (i.e., with some beats coinciding with silences, thus requiring endogenous processes to perceive a beat) and the other unsyncopated (i.e., with tones coinciding with all beats, thus allowing exogenously driven beat perception) (task 1). Participants were afterwards asked to tap the beat of the rhythms (task 2). In a later session, the same individuals completed a finger-tapping task assessing the degree to which they predicted timing variations while synchronizing with tempo-changing auditory sequences (task 3). This measure was obtained by comparing the inter-onset intervals (IOI) between tones in the sequence with the inter-tap intervals (ITI) at lag 0 (vertical lines) and lag -1 (oblique lines).

Spectrum of the stimulus rhythms’ envelope (in blue) and corresponding EEG (in black, averaged across participants and all channels) as recorded from task 1.

The unsyncopated and syncopated rhythms were played at four distinct tempi, from slow (top) to fast (bottom), with beat frequencies at 0.6 Hz, 1.25 Hz, 2.5 Hz and 3.8 Hz, respectively (arrows). Note that at all tempi, the spectrum corresponding to the unsyncopated rhythm shows a prominent peak in acoustic energy at the beat frequency, in contrast to the syncopated rhythm. The topographical distribution of this activity was generally frontocentral for all rhythms and tempi (color scale ranges correspond to the y axis, with hot colors indicating high values).

Panel A illustrates that synchronization accuracy improves (mean signed asynchronies closer to zero when synchronizing to the beat) with increasing strength of selective neural entrainment to the beat. Panel B illustrates that individuals with high prediction indices show high neural entrainment to an endogenous beat. Note that 3 from the 18 participants did not return for task 3 and that 2 from the 18 participants were excluded from task 2 analyses because they did not tap as instructed.